HIV is a retrovirus that causes immunosuppression in humans (HIV disease), and leads to a disease complex known as the acquired immunodeficiency syndrome (AIDS). HIV disease is characterized by progressive functional deterioration of the immune system. The treatment of HIV disease has been significantly advanced by the recognition that combining different drugs with specific activities against different biochemical functions of the virus can help reduce the rapid development of drug resistant viruses that were seen in response to single drug treatment. However, even with combined treatments, multi-drug resistant strains of the virus have emerged. There is therefore a continuing need for the development of new anti-retroviral drugs that act specifically at different steps of the viral infection and replication cycle.
The integrase (IN) enzyme is an example of such a specific target. This enzyme catalyzes the insertion by virally-encoded integrase of proviral DNA into the host cell genome, which is the mechanism by which HIV and other retroviruses are introduced into human T-lymphoid cells. For HIV-1, this process is mediated by a 32 kD virally encoded integrase, having conserved sequences in the HIV long terminal repeats (LTR)1. Following reverse-transcription in the cytoplasm of infected cells, integrase cleaves two nucleotides from each of the viral DNA ends which contain a highly conserved CA motif. The cleaved DNA migrates to the nucleus as a part of a large nucleoprotein complex, where the integrase catalyzes the insertion of viral DNA into a host chromosome by a direct transesterification reaction.
In vitro assays have previously been developed to identify integrase inhibitors,2,3 and have permitted the discovery of diverse classes of drugs that inhibit integrase.5,6 However, the drugs discovered by these assays have not been highly selective and potent inhibitors of the integrase enzyme. Many of these drugs have additionally been non-selective inhibitors of reverse transcriptase or HIV protease, which limits their usefulness in combination therapy directed to different specific steps of the retroviral life cycle.
One class of reported integrase inhibitors is catechol-containing hydroxylated aromatics, which are non-selective integrase inhibitors that can also cross-link proteins6 and chelate metals7. Non-catechol containing compounds, however, have been found to be cytotoxic, perhaps because they are unable to form reactive quinones. Such generalized cytotoxicity is a disadvantage, because it can affect host cells without being selective for retroviral eradication or inhibition.
Some hydrazides have been reported to be novel noncatechol-containing inhibitors of integrase. Structure-activity relationship studies among these inhibitors have indicated that the salicyl moiety is required for activity. Some benzothiazepine derivatives (such as diltiazem) have been reported to have lymphocyte protectant activity in U.S. Pat. No. 4,861,770, and benzodiazepine hydrazide derivatives have been reported to inhibit HIV integrase in WO 98/18473. However, a specific anti-integrase inhibitor with minimal cytotoxic activity is not yet available.